The present disclosure relates to digital manufacturing systems for building three-dimensional (3D) models. In particular, the present disclosure relates to platform assemblies for use with digital manufacturing systems, such as deposition-based digital manufacturing systems.
Digital manufacturing systems are used to build 3D models from digital representations of the 3D models (e.g., STL format files) using one or more layer-based additive techniques. Examples of commercially available layer-based additive techniques include fused deposition modeling, ink jetting, selective laser sintering, electron-beam melting, and stereolithographic processes. For each of these techniques, the digital representation of the 3D model is initially sliced into multiple horizontal layers. For each sliced layer, a build path is then generated, which provides instructions for the particular digital manufacturing system to form the given layer. For deposition-based systems (e.g., fused deposition modeling and ink jetting), the build path defines the pattern for depositing roads of modeling material from a moveable deposition head to form the given layer.
For example, in a fused deposition modeling system, modeling material is extruded from a moveable extrusion head, and is deposited as a sequence of roads on a platform in a horizontal x-y plane based on the build path. The extruded modeling material fuses to previously deposited modeling material, and solidifies upon a drop in temperature. The position of the extrusion head relative to the platform is then incremented along a vertical z-axis, and the process is then repeated to form a 3D model resembling the digital representation.
Movement of the deposition head in the x-y plane, and movement of the deposited layers along the z-axis on the underlying platform are desirably controlled such that each layer of material is uniformly deposited. This typically requires the deposition head to remain at a constant and uniform distance above the platform during a deposition process. Thus, ideally, the deposition head remains in the same x-y plane over its operational range of motion, and the underlying platform exhibits a truly planar surface. This allows the deposition head to remain at the same height along the z-axis relative to the platform over its operational range of motion. However, due to manufacturing limitations, the gantry that supports the deposition head may not necessarily move the deposition head in a perfect x-y plane, and the platform may not necessarily exhibit a truly planar surface. These limitations may also increase as the size of the platform and the area over which the gantry must cover increase, such as in layered deposition systems designed to produce large 3D models.
The varying heights between the deposition head and the underlying platform may have undesirable effects on the deposition patterns of the modeling and support materials, such as variations in layer thicknesses and variations in fine-feature resolution. This is particularly true for initially deposited layers of modeling and/or support materials that desirably bond to the underlying platform. Current corrective measures for reducing such variations involve reorienting the entire platform in an attempt to keep the minimize the variations. Such corrective measures, however, are inhibited as the size of the platform increases because the freedom to rotate the platform is significantly reduced. Additional corrective measures may involve depositing base layers (e.g., of support materials) prior to depositing the modeling material for the 3D model. While these techniques are suitable for mitigating the non-planar profiles, they may require additional time and costs for forming the base layers. As such, there is a need for systems and techniques for maintaining uniformity of the distances between depositions heads and underlying platform.